Method of debonding a brake lining from a brake shoe



1962 J. STEIN 3,058,870

METHOD OF DEBONDING A BRAKE LINING FROM A BRAKE SHOE 2 Sheets-Sheet 1 Filed Feb. 15, 1956 llnite ZQLQS This invention relates to the debonding or the removal of brake linings from brake shoes preparatory to the bonding of a new lining.

The lining is usually bonded to a brake shoes adhesively by a heat hardened organic binder. In debonding the shoe heat is applied so that the binder is decomposed and oxidized. Apparatus, in accordance with the teachings of the prior art, for debonding the brake linings from brake shoes, is typified by Batchelor Patent 2,711,775 and it appears desirable to use this patent at a starting point in explaining the invention disclosed herein.

In accordance with the Batchelor patent the shoe is mounted on a wheel and heated by radiant heat from a plurality of radiators extending along the flanges of the shoe. The wheel on which the shoe is mounted is held in one of its extreme positions for about twenty seconds while the heat is applied and then moved to the other extreme position while heat continues to be applied, the movement consuming another twenty seconds. Since approximately twenty seconds would be consumed in mounting and removing the shoe from the wheel, the total time for debonding a shoe is of the order of one minute.

After a shoe is debonded the metallic base remaining is subjected to cleaning in a shot blasting chamber and then it is coated with cement -by dipping and a new lining is bonded to it. But while a shoe is in use on a vehicle it tends to come into contact with the grease on the Wheel to which it is applied and with the braking fluid and thus has a substantial deposit of greasy and oily material on its surface. This material must be removed before the blasting and cementing operations are performed because it tends to render the shot in the shot-blasting chamber sticky and ineffective, and also because any greasy or oily deposit on the surface of the base tends to prevent the adhesion of the cement.

The prior art apparatus typified by Batchelor has the disadvantage that its debonding time is too long; sixty shoes per hour is inadequate to meet the demands of a modern relining plant. In addition, this prior art has the disadvantage that the shoes must be degreased before the blasting and cementing operation.

It is, accordingly, broadly an object of this invention to provide debonding apparatus and a debonding method, in the use and practice of which it shall be feasible to debond a brake shoe in a substantially shorter interval than the debonding time necessary in accordance with the teachings of the prior art.

Another object of this invention is to provide a method and apparatus for debonding a brake shoe, in the use and practice of which the base from which the lining is removed shall be thoroughly purged of any greasy or oily material.

A more specific object of this invention is to provide a novel conveyor furnace which while having other uses is particularly suitable for the debonding of a brake shoe in the practice of this invention.

Another specific object of this invention is to provide a novel conveyor chain.

In accordance with this invention, heat is concentrated on the opposite ends of the brake shoe to cause the lining to curl away at the ends from the base to which it is bonded. This results from the forces applied within the brake lining as it tends to expand when heated. While the heat is being concentrated on the ends of the shoe 3,583?) Patented Oct. 16, 1962 and the lining is curling away from the base, the shoe is also heated throughout. This causes the binder to decompose and become plastic. The resulting pressure blasts the lining away from the base and the lining drops off. In the preferred practice of this invention, the heating of the base then continues until all of the greasy and oily material which has adhered to the surface of the base has been oxidized.

In accordance with the preferred practice of this invention, the concentrated heating is effected by conveying the brake shoes through a tunnel or furnace into which flames from a plurality of nozzles project. The brake shoes are so positioned while being moved that the flames contact the opposite ends of the shoes thus producing the required concentrated heating of the ends. The nozzles on one side of the tunnelare staggered with respect to the nozzles on the other side. This staggering has several advantages. First it is advantageous as regards the operation of the furnace in that the flame emitted by one nozzle does not tend to blow out the flame of the nozzle opposite it. Further, because the nozzles are staggered, the heat is concentrated on the ends of the brake shoe alternately and this mode of heating has been found to be effective in producing the curling and the removal of the lining. It has also been found to be more effective in removing lining to concentrate a plurality of successive heat blasts in rapid succession against the ends of the brake shoe than to apply the heat shots more slowly but to both ends simultaneously.

The tunnel has a refractory lining which is heated by the flames from the nozzles to a high temperature and the radiation from which heats the shoes throughout while the concentrated heat is being applied on their ends. The heating throughout has the effect of causing the binder to decompose and explode and the lining to drop from the bases. In the practice of this invention, each shoe is so moved through the flames and is so heated that the lining drops away from the base before the shoe has reached the end of the tunnel. While the lining is being removed the greasy and oily materials are oxidized by the flames; thus when a base has reached the end of the tunnel it is completely degreased. The shoe then continues moving while it is subject to a cooling air draft for a predetermined interval allowing it to cool. After this interval the shoe drops into a trough. When the shoe is ready to drop into the trough it is sufficiently cooled so that it is not damaged by the shock of being dropped. The shoe is now ready for the shot blasting chamber.

In the practice of this invention, the shoes are moved continuously through the flames and it has been found that because of this movement the instantaneous temperature to which the brake shoes are subjected may be substantially higher than the temperature to which brake shoes may be subjected when they are maintained continuously in a heating region. Further, the lining is effectively removed from a brake shoe and the base is effectively purged of grease and oil by movement through the tunnel or furnace at a high rate and thus the rate of debonding shoes is high. In fact, in the practice of this invention, it has been found that, depending on the character or" the brake shoe, from 500 to 700 shoes may be debonded per hour. The high rate of debonding and the high temperature are thus compounded factors in conferring advantage on the method according to this invention. The higher the rate the higher the temperature may be and the more effective the debonding and the oxidation and the higher the temperature the higher the rate.

The novel features considered characteristic of this invention are described generally above. The invention itself both as to its organization and its method of operation, together with additional obiects and advantages thereidler. The drive 99 is of, will be understood from the following description of a specific embodiment when read in connection with the accompanying drawings in which:

FIGURE 1 is a view partly in transverse section showing a preferred embodiment of this invention;

FIG. 2 is a view in section taken along II-II of FIG. 1;

FIG. 3 is a view in section taken along III-11 of FIG. 2;

FIGS. 4a, 4b and 4c are graphs showing the temperature distribution in a furnace or tunnel in accordance with this invention; and

FIG. 5 is a fragmental view showing a chain used in the practiceof this invention.

The apparatus shown in FIGS. 1, 2 and 3 includes a support comprising spaced pairs of vertical angle irons 11 and 13. Across the top of each pair of irons 11 and 13 a long angle bar 15 and 17, respectively, is secured by angle brackets 19. The bars 15 and 17 extend a greater distance on one side than on the other and are braced by cross angle irons 21 on this side. A platform 23 is secured between the angle irons 11 and 13 near their lower ends. A trough 24 is pivotally supported from the angle irons 11 and 13 on one side.

A tunnel or open end furnace 31 having a top 33, a base 35 and side Walls 37 and 39 of refractory material is mounted on the bars 15 and 17. A plurality of openings 41 and 43 are provided in the sidewalls 37 and 39, respectively, the openings 41 in one wall 37 being staggered with respect to the openings in the other wall. Each opening 41, 43 is flared inwardly. Opposite each opening (41, 43) on the outside of the tunnel a nozzle 51 is mounted on a bracket 53. While nozzles of many types may be utilized, in accordance with the preferred practice of this invention, the Sticktite flame retention nozzles sold by Maxon Premix Burner Company of Muncie, Indiana, is preferred. This nozzle is disclosed on pages 1201 and 1202 of the Maxon Bulletin 1200. The mouths of the nozzles 51 are so dimensioned and spaced relative to the openings 41 and 43 and the brackets 53 are so shaped that there is an air gap between the nozzles 51 and the boundaries of the openings 41, 43.

The nozzles 51 are supplied with gas from a manifold 61 which is itself supplied through a tube 63. Gas and air in a ratio of approximately 10 parts of air to 1 part of gas are transmitted through the tube 63 by a blower and mixer 65 mounted on plate 23. This gas is ignited at the nozzles 51 and produces a broad flame at each nozzle which extends into the associated opening 41 or 43 in the Wall of the tunnel and flares out into the tunnel. As the combustion gases in the flame are projected into the tunnel through the openings 41 and 43, they carry with them air which flows around the mouths of the nozzles 51 into the openings in the tunnel and assures the complete combustion of any material oxidized in the tunnel.

A hood 71 is mounted on the top 33 of the tunnel and extends over and overlaps the open ends of the tunnel. The hood includes a sheet metal outer casing 72 Within which a roof 73 of refractory material is secured. The casing 72 extends over the ends of the roof 73. The roof 73 of the hood opens into a flue 75. A wall of chains 81 extends from an angle bracket 77 secured to the roof 73 on one side and another wall ofchains 82 extends from the end of the tunnel on the other side. An enclosure or curtain 85 of heat resistant board is supported by the extension 8 7 on the-latter side. The flue 75 extends centrally in a transverse direction with reference to the hood 71 but is displaced longitudinally towards the side of the enclosure 85 with reference to the tunnel. 7

Between the ends of the angle bars 15 and 17 a pair of sprocket wheels 91 and 93 are mounted on suitable bearings 95 and 97, respectively. One of these sprocket wheels 91 is driven from a variable speed drive 99 through a sprocket chain 101. The other sprocket wheel 93 is an mounted on the plate 23. A sprocket chain conveyor 103 is mounted in engagement with the sprocket wheels 91 and 93 extending through and under the tunnel between the bars 15 and 17 and is driven by sprocket wheel 91 and as it is so'driven passes over the idler sprocket wheel 93 and advances through the tunnel in the direction from wheel 93 to wheel 91.

On the chain a plurality of brake shoe holders 111 are mounted. Each of these holders consists of a pair of angle brackets 115 and 117 bolted to each chain link 118 and held together by a tie bar 120. The sides 122 of the angle bars extending away from the link 118 are slotted. A brake shoe 121 may be mounted on each of the supports 111, either with the web 123 extending through the slots 125 (as in FIG. 3) or with the flange 127 extending through the slots. In either case the brake shoe lies loosely in the slots 125 with its ends extending in both directions from the slot so that they project into the flames produced by the nozzles 51.

Since the conveyor 103 may at times sag under the weight of the brake shoes 121, a supporting bracket 131 is provided within the tunnel which extends under the conveyor and over which the conveyor and shoe supports may slide without damaging the lining on the floor of the tunnel.

In the use of the apparatus the flames are ignited in the nozzles 51 and after stable conditions are reached the conveyor 103 is started. The drive 99 is set so that the speed of the conveyor 103 is suitable for the shoe being delined. The operator then stands near the feed-in end of the tunnel and places the shoes 121 in the supports 111 as they pass by. The shoes are then moved into the tunnel and the ends of the shoes pass successively and alternately through the flames produced by the nozzles 51. The brake lining is then curled as shown at 141. The shoes are also heated throughout and eventually the lining drops from its base. Since the brake shoes 121 are held loosely in the holders 111, there is no tendency to deform or distort the brake shoes by overheating, even if over-heating tended to occur. But in the practice of this invention the shoes are moved through the tunnel at so high a rate that there is no tendency to overheat. The lining usually drops away from the base of each shoe before the shoe reaches the delivery end of the tunnel. It has been found that depending on the speed of the conveyor 103, the temperature in the tunnel, and the character of the shoe, the lining drops oif at some point in the region between the second nozzle 51 on each side and the end of the tunnel. While the shoe is being conveyed through the tunnel, the greasy and oily materials on its surface are entirely oxidized. The heating and oxidation are supported by the air sucked into the tunnel at the nozzles 51 and also by the air draft through the ends of the tunnel. Because the feed-in end of the tunnel is relatively open and the delivery end is relatively closed there is a greater draft into the tunnel on the side into which the work moves than on the other side. The conveyor 103 extends -a substantial distance beyond the exit end of the tunnel so that the shoes are cooled by the draft of air through the exit end before they reach the end of the conveyor. When the shoes reach the end of the conveyor they drop into trough 24.

The flames from' the nozzles 51 not only shock heat or concentrate the heat on the ends of the brake shoes 121 but also by radiation and convection heat the refractory materials in the sides 37 and 39, roof 33 and base 35 of the tunnel and the radiation from this refractory material provides additional continuous heat for the shoes. In addition, the draft of air passing in through the chain 81 and out through the chain 82 tends to produce a draft of the combustion gases into and through the hood 71 and up through the flue 75 or stack 75. By the cooperation of the air-draft flowing into the hood through the shield and the flames Within the tunnel which are caused to flow into the hood the hydrocarbons which are produced in the tunnel are entirely oxidized and there is substantially no smoke emitted from the flue. Thus the apparatus can be used in communities which have smoke control laws or ordinances. The refractory roof 73 is also heated to a high temperature and helps to oxidize any residual hydrocarbons which may flow into the hood.

In apparatus, in accordance with this invention which has been constructed and found to operate satisfactorily, the tunnel is 48 inches long, 12 inches high and 15 inches wide (inside dimensions) and there are six nozzles, three on each side. The spacing between successive nozzles on each side is 16 inches. The end nozzle on one side is spaced 10 inches from the entrance end of the tunnel and the end nozzle on the opposite side is spaced 6 inches from the entrance side of the tunnel. The shoes are conveyed substantially through the longitudinal center of the tunnel. With these nozzles burning commercial heating gas in the operation of the apparatus, the temperature distribution along the tunnel is shown in graphs 0, b, and c of FIG. 4. In each of the graphs of FIG. 4, temperature is plotted vertically and the position from the entrance end of the tunnel in inches is plotted horizontally. The temperature is in degrees Fahrenheit.

Graph 4a shows the distribution along the center of the tunnel in the region of the nozzles. Graphs 4b and 40 show the distribution near the bottom of the tunnel on both sides. The words left and right are used with reference to an observer facing the feed-in end of the tunnel. It is seen that the temperature distribution is highly irregular and it is this irregular distribution which tends to produce the curling efiect which is important in the removal of the lining from the shoe.

With the apparatus above described 500 to 700 shoes may be debonded per hour. Assuming 600 shoes per hour as a fair average, it is seen that each shoe moves through the tunnel in of an hour or in 6 seconds. The speed of each shoe is then 8 inches per second and at these speeds the shoes are not damaged in the hightemperature regions of the tunnel.

While a specific embodiment of this invention has been disclosed herein, many modifications thereof are feasible. This invention, therefore, is not to be restricted except insofar as is necessitated by the spirit of the prior art.

I claim as my invention:

The method of debonding a brake lining from a brake shoe to which said lining has been adhesively bonded by means of an interposed heat hardened organic binder, which comprises passing both ends of said brake shoe which are generally transverse to the long dimension of said shoe through discrete regions of intense heat, to concentrate heat on the ends of said brake shoe sufficiently to raise said ends to a temperature such as to cause the ends of said lining to curl away from the metallic base of said shoe, each of said ends being passed through a plurality References Cited in the file of this patent UNITED STATES PATENTS 888,815 Jones May 26, 1908 1,053,162 Denney Feb. 18, 1913 1,549,494 MacDonald Aug. 11, 1925 1,872,210 Wunderlich Aug. 16, 1932 1,949,716 Harsch Mar. 6, 1934 2,062,642 Darrah Dec. 13, 1936 2,274,677 Eberhart Mar. 3, 1942 2,279,689 Lerner Apr. 14, 1942 2,337,603 Hertzberg Dec. 28, 1943 2,367,429 Rauen Ian. 16, 1945 2,393,521 Duncan et al Jan. 22, 1946 2,494,281 Batchelor et al. Jan. 10, 1950 2,539,135 Hess Jan. 23, 1951 2,608,504 Meyer et a1. Aug. 26, 1952 2,655,976 Lovin Oct. 20, 1953 2,675,051 Schnebelen Apr. 13, 1954 2,677,408 Wesstrom et al May 4, 1954 2,689,372 Goulding et a1. Sept. 21, 1954 2,711,676 Richardson et al June 28, 1955 2,711,775 Batchelor et al June 28, 1955 2,711,984 Kingman June 28, 1955 2,788,958 Tilden Apr. 16, 1957 

